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The nozzle is one of the most important points of interest in most 3D printers. It defines what can be done and what can’t be done with a 3D printer.

Nozzle width in relation to corners and wall thickness

In 3D printing, no real sharp corners are allowed; the minimum radius of a corner is equal to the radius of the nozzle. In other words: a 0.5mm nozzle is never able to make corners sharper than 0.25mm in radius.

In most cases even this is optimistic (since the nozzle needs to ‘push’ the layers onto each other), the printing diameter (also called printing width) can be 20-30% larger. In the case the printing diameter is 20% larger, a 0.3mm radius corner is the best the printer can print with a 0.5mm nozzle.

Also, the wall thickness should be in multiples of the printing width. So in the case above, the minimum wall thickness is 0.6mm. A wall thickness between 0.6mm and 1.2mm results in 0.6mm or 1.2mm wall thickness. As soon as two perimeters in width are reached, it depends a bit on the type of slicer you use. Some slicers fill in the gap nicely, others only handle multiplies of the printing width.

projected vs printed

The situation depicted above is a common problem most printers have. The red rectangle is the surface (or cut through) we would like to print, the green line is the line printed by the nozzle. The problem becomes clear quite easily: the red rectangle can’t be covered by the nozzle.

Not only the corners, as we discussed earlier, but also on the inside a part of the red rectangle is left untouched. This often leads to a weak print.

The basic rules

The basic rules of 3D printing thin walls and sharp corners can be summarized in the following points:

  1. Preferably, use wall thicknesses in multiples of the printing width when designing.
  2. The sharpest corner you can make is roughly 125% the radius of the printing diameter.
  3. There is no reason for saving material by using thin walls, by selecting a proper infill, the material is saved anyway. So use solid bodies whenever possible.
  4. If the design is there and you need to print it anyway, try to use as little perimeters as possible (while still getting a nice looking print).

The flip side of the coin

With all these issues, is there no easier way? Like using a smaller nozzle? Unfortunately it isn’t that easy. A smaller nozzle results in a longer printing time, but also more layers. More layers often results in a weaker print, since the layer adhesion is the weakest link in most parts. Also small nozzles tend to result in more warping. (And warping is our worst enemy since it creates cracks and bad prints.) A smaller nozzle is not always a better choice. Our advice is to match the design and the nozzle you are using carefully. This can be tricky, but at the end creates the strongest possible prints.

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